As a general rule, higher impedance headphones require more power from the headphone output of your interface than lower impedance headphones.
If unsure of what to purchase follow these general guidelines:
- For all Bus Powered Scarlett interfaces, iTrack Solo and Saffire 6 USB look for headphones with a maximum impedance of 200 ohms.
- For all mains powered Scarlett interfaces (6i6, 8i6, 18i6, 18i8 and 18i20) look for headphones with a maximum impedance of 250 ohms.
- For all Clarett (USB and Thunderbolt variants) and Red (Thunderbolt) interfaces, headphones with impedances of up to 600 ohms will be fine.
Closed-back headphones are useful to prevent bleed if worn by vocalists or by performers near microphones whereas open or semi-closed headphones are ideal for control room use and for long sessions.
As far as the "will this exact combination of models be loud enough for me" question the answer will vary somewhat from person to person, even for the same model units and headphones, as there are other factors to consider (how loud is the source material you will be listening to, how quiet/loud is the environment you will be listening in etc.).
For additional information see this article What is impedance and how does it affect the volume of my headphones?
If you need any further assistance then please Contact Technical Support